Modern mobile communication devices shall provide the functionality of transmitting and receiving RF (Radio Frequency) signals virtually at the same time. Duplexer circuits are used to separate TX (transmit) signals from RX (receive) signals and provide a high isolation of the respective signal paths. Further, it is preferred that duplexers provide a highly linear behavior, robustness against antenna mismatch, a high integration density—i.e. small spatial dimensions—and a small number of electric components.
However, the current trend towards devices providing more different frequency bands and transmission modes is contrary to small spatial dimensions and—due to mutual interaction—to good electrical properties.
From patent application US 2013/0234806, duplexer circuits that provide superior isolation properties are known. But for the high isolation, a complex network of conventional duplexers and hybrid circuits is needed.
Further, WCDMA (Wideband Code Division Multiple Access)-standard already supports RX diversity functionality. According to the LTE standard, RX MIMO (Multiple Input Multiple Output) functionality is mandatory.
Thus, mobile communication devices need further circuits such as filters, amplifiers and/or switches to comply with these standards. However, as stated above, integration of such further circuitry is problematic.
What is needed is a circuitry that can be used in mobile communication devices, that complies with the standards and is compatible with further signal paths without jeopardizing already simultaneously achieved geometric compactness and good electrical properties.
Accordingly, it is an object of the present invention to provide such circuitry and improve mobile communication devices.
Such circuitry (namely a multiplexer) and such devices are provided by the independent claims. Dependent claims define preferred embodiments.